Conventionally, an image processing technology called relighting is used in image processing and others to create an illumination environment different from that in image shooting and perform again illumination and drawing processes.
Information required for relighting is roughly divided into the shape of a subject, the reflection characteristics of the subject, and the position of a light source. They are the same as elements for use in drawing general three-dimensional computer graphics. The shape of the subject is obtained using a method by which the depth of the subject is estimated by stereo matching using a plurality of cameras, and a model is reconstructed from an aggregate of three-dimensional coordinates corresponding to the pixels, for example. To obtain the reflection characteristics of the subject and the position of the light source, a method using the reflection of the light source on a spherical mirror has been proposed, for example.
In addition, to generate a proper relighting image, parameters such as the number of light sources, and the types, placements, and light intensities of the light sources need to be set in a proper manner. For example, Patent Document 1 discloses that only the intensities of the light sources are automatically adjusted. In addition, Patent Document 2 discloses that lights generated at random are listed and used for rendering in a low-frequency area.